Spear phishing is a kind of phishing attack that targets a specific victim. Rather than casting a wide net, hoping one in a million will fall for the trick, spear phishing attackers spend a great deal of time making their schemes appear completely legitimate in an attempt to fool their victims into opening a malicious file.

Spear phishers are often agents of foreign governments that do reconnaissance work on their victims to figure out what will make them believe an e-mail is coming from a trusted source. The attackers will often spoof addresses of loved ones, friends or bosses.

"It's spooky when you see one," said Greg Hoglund, CEO of security company HBGary. "A person took the time to do research on one person and make it look very personal."